Method and apparatus for heating metallic wire, bars, and strips



April 13, 1954 s. E. LEONARD 2,675,461

METHOD AND APPARATUS FOR HEATING METALLIC WIRE BARS AND STRIPS 3 Sheets-Sheet 1.

Filed July 29, 1949 47 INVENTOR. SAMUEL E Lao/men BY Ar roe/vs ya April 13, 1954 s. E. LEONARD 2,675,461

METHOD AND APPARATUS FOR HEATING METALLIC WIRE, BARS, AND STRIPS Filed July 29, 1949 '3 Sheets-Sheet 2 2.? Y 2/ 1.9 w U Q) O O O (D O T25 22) INVENTOR. SAMl/EL E [EON/1RD April 13, 1954 s. E. LEONAIEQ'D METHOD AND APPARATUS FOR HEATING METALLIC WIRE BARS AND STRIPS 3 Sheets-Sheet 3 Filed July 29, 1949 zlvmvroza. SAMUEL E 150M420 BY Patented Apr. 13, 1954 METHOD AND APPARATUS FOR HEATING METALLIC WIRE, BARS, AND STRIPS Samuel E. Leonard, Shaker Heights, Ohio Application July 29, 1949, Serial No. 107,604

This invention relates to the heat-treating of fine wire and bars and strips of metal.

It is a well-known fact that it is difficult to heat wires of small diameters, small sizes of bars and thin strips of metal by electric induction, due to the fact that the extremely small cross section of the work does not afiord sufiiciently large circumferential extent for the flow of induced current without such alternating induced currents interfering with and counteracting each other and thereby reducing the amount of induced current and hence the amount of heat in the wire or other work of small size.

The principal object of my present invention is to provide an eificient method and apparatus for heating moving wires, bars and strips of metal especially those of both high and low carbon iron and steel, although my invention is capable of being used in the heating of non-ferrous metals also.

More specifically, the general object of my present invention is to devise an improved means for heat-treating metal wire, bars and strips, this object being accomplished by moving the wire,

bar or strip through a field of electric induction.

A further object is to devise a means for guiding or directing the wires, bars or strips longitudinally through a field of electric induction or to cause the same to be coupled to the field of electric induction and to thereby produce a more efiicient method in the heating and handling of the work.

A further object is to devise such a means for guiding the work longitudinally through the field of electric induction or for causing the same to be coupled to the field of electric induction so that it will be possible to operate over a wider range of frequencies with efiiciency, than would be otherwise possib1e,"-and to be able to handle a wider rangeof gauges of metal.

A further object is to devise a means whereby metal wire, bars and strips may be heated to temperatures above the Curie point.

A further object is to devise a guide means for the work, with means for producing heat by both electric induction and conduction while the work is in the field of electric induction or is coupled to the induction field.

A further object is to devise a work-guide means with provision for increasing the effective circumferential extent of the metallic area of the work while in the field of electric induction, this being especially advantageous in the case of work of extremely small cross section. v

Another object is to devise a method of heat- 7 Claims. (01. 219-) 2 treating metal wire, bars and strips, that is capable of being adapted to various conditions of the work by designing particular equipment according to the requirements of a given set of conditions, as will more fully appear hereinafter.

In practicing the present invention, I may use the generators disclosed in my United States Letters Patent No. 2,205,424 and No. 2,205,425; and it is assumed that this brief word of reference to my prior patents will suffice for the present purposes. Also, it is to be assumed that the frequency used will be properly tuned to the load circuit. As will be observed from the above statement of objects, the present invention relates to an improved method and apparatus for handling the metal wires, bars and strips during the performance of the heat-treating process.

Other objects will appear from the following description and claims when considered together with th accompanying drawings.

Fig. 1 is an elevation of one form of guide means for wires which are moved longitudinally through a field of electric induction, the rest of the electric system being indicated diagrammatically;

Fig. 2 is a transverse sectional view of the same form of guide means as is shown in Fig. 1;

Fig. 3 is an elevation of another form of guide means with provision for moving the wires along the inside thereof, whereas in Figure 1 the wires are moved along the outside of the guide means;

Fig. 4 is a transverse sectional view of the guide means indicated in Fig. 3;

Fig. 5 is an elevation of another form of guide means with provision for moving the wires along the inside and through the central, middle part thereof;

Fig. 6 is a transverse sectional view of the same;

Fig. '7 is a top plan view of a guide means for a metal strip or strips; 7

Fig. 8 is an elevation of the same;

Fig. 9 illustrates diagrammatically a form of device for moving a plurality of pieces of work simultaneously through a plurality of successively arranged fields of electric induction;

Fig. 10 is an elevation of another form of guide means, which is of rotatable form;

Fig. 11 is an end elevation thereof; I

Fig. 12 is an elevation of still another form of uide means;

Fig. 13 is a transverse sectional view thereof;

Fig. 14 is an end view of another form of guide means;

Fig. indicates the surface thereof in fiattened form for purposes of illustration;

Fig. 16 is an. enlarged view of one of the guide posts employed in the form of device indicated in Fig. 14.

Fig. 17 is a side elevation of an inductor block with guide means therewithin for the work; and

Fig. 18 is a sectional view thereof.

It is to be understood that the present form of disclosure is merely for the purpose of illustration and that there might be devised various modifications thereof without departing from the spirit of my invention as herein set forth and claimed.

When the gauge of the work is sufficiently large in cross section so that the circumferential extent of the outer surface thereof will permit induced current without the objection above noted, the individual pieces of work, either wire, bar or strip, may be directed through a guide means with straight parallel grooves extending lengthwise thereof, as illustrated in Figs. 1 and 2 of the present drawings. In Fig. l the guide I is a cylindrical form or metal or ceramic body with spaced parallel grooves 2 extending lengthwise along the outside thereof so as to accom- I modate the wires W which are moved therealong by any suitable means that is well known in the industry. This guide I will be positioned within the field of the multi-turn electric induction coil 3 which is here indicated diagrammatically in circuit with the secondary coil 4' of an air-core transformer whose primary 5 is in circuit with the electronic generator indicated diagrammatically at 6, as for instance one of those disclosed in my prior patents above noted. Here, as also in the several other forms of my present invention, the work circuit including the secondary coil 4 and the work coil 3 may be water-cooled; and this circuit is tuned by means of the condenser 1, here indicated as being arranged in parallel although it might be in series, and it is to be understood that the same circuit arrangement including the generator, the primary and secondary coils and tuned work circuit, is employed in each of the several following instances although not fully indicated in each instance.

When the body of the guide I is made of ceramic material, the wire W will be heated by electric induction only, with loose coupling. When the body of the guide I is made of metallic material, as for instance copper, high current is induced in the copper body and is transferred to the wire W in the form of very close coupling;

and the wire W or other work is heated by. induction as well as by direct contact and high current conduction.

Instead of having the guide grooves upon the outside, as in Figs. 1 and 2, they may 'be provided upon the inside of a substantially cylindrical hollow body 8 of ceramic material, as indicated at 9 in Figs. 3 and 4 of the present drawings. This will be a loose coupling.

In Figs. 5 and 6 I have indicated a substantially cylindrical body I I of electric insulation material with individual passages I2 converging from the entrance end thereof towards the middle center thereof and also with individual passages I3 diverging from the middle center part of the guide to the exit end thereof. With this form of guide means, the wires W are led into the entrance thereof through the individual passages I2 and are converged at the middle center part into compact contactual parallel arrangement, and the moving wires will leave the guide through the separate passages I3. This arrangement is intended principally for those wires whose individual circumferential extent is so small that heretofore there has been substantial hindrance to the induction of current, as above explained. This entire guide will be located within the field of electric induction, in the same manner as indicated in Fig. l, and with the wires in compact contactual parallel arrangement, the large outside aggregate circumference thereof will relieve or preclude the hindrance due to the small circumferential area of an individual wire, as above pointed out. Then, as the outer layer of wires in this compact group is heated to the Curie point, appriximately 1400 degrees Fahrenheit, and due to the loss of the magnetic property of the outer layer of this combined group of wires, the inductive field about the group of wires will move inwardly towards the center thereof and this will continue until the centermost wire at the very core of the group of wires has been reached. In this form of device the increase in heat will cause an expansion in the diameter of the work, which in turn will cause an improved contactual relationship. As above explained, the limited circumference of such a small single wire would ordinarily hinder the phenomenon of induction; but in the present situation the inward radiation of heat from the outer layers of wires in the group serves to gradually and continuously increase the temperature of the inner layers of wires, whereby the heating of the center wire by induction is augmented by radiation and conduction of heat inwardly and consequently the inner-most wire will be heated to the desired point, with the result that the ordinary hindrance to the heating of a single fine wire is overcome. It may be said that, with this form of guide means, there will be heating of the wires by electric induction and also by radiation and conduction of heat inwardly while passing through the middle part of the guide means, this being a semi-loose coupling.

Instead of the wires being grouped in such compact, contactual parallel arrangement in the middle part of the guide, as just described, they may be grouped in a hollow circular arrangement with each wire contacting only the two adjacent wires upon the opposite sides thereof, while passing through the middle part of the guide. The large over-all diameter that is thus formed, allows circumferential induced currents to flow even at low frequencies because the current flows across the cross section of the wire and the induced current path now is the circumference formed by the added diameters and the total diameters of this combined arrangement make it couple efilciently. As a result, heat is caused by greatly increased currents across the cross section of each wire or the like whereas if the wire or the like were alone in the induction field, the smaller current would flow only around its own circumference. In this arrangement also, the aggregate circumferential area of the wires will be substantially increased. and thus the hindrance to the heating of a wire of small diameter by electric induction will be relieved accordingly. It should be noted also that in such an arrangement of the wires or the like, the expansion of their diameters by the heat serves to produce better 'wire-to-wire contactual engagement between the same. Also, this heating by electric induction will be au mented by radiation and conduction of heat by virtue of the contactual arrangement of the wires or other work.

There may be designed also a guide means of I this same character, as just described, for grouping bars of extremely small cross section as they travel through the middle part of the guide.

Likewise there may be provided a guide i5 with a groove It for directing a plurality of strips S in superimposed contactual relation through the middle part of the field of electric induction. Idle rollers I! may be provided at the two ends of the guide means for the strips, as indicated in Figs. '7 and 8 of the present drawings. With a ceramic form of guide means, there will be a loose coupling; and when there is employed a hollow copper form of guide, there will be obtained a close coupling.

When the fine wires, rods or strips are brought into contactual relation within the guide means, as pointed out in Figs. 5, 6, 7 and 8 of the accompanying drawings, these work units may be said to be in solid mesh. It might be pointed out that, even when the units of work are grouped in only circular arrangement and not in complete mesh, there will be afforded a greatly increased combined circumferential extent and consequently the ordinary hindrance to the induced current will be correspondingly overcome as above explained.

In Fig. 9 I have illustrated diagrammatically another form of guide device for use in the heating of a plurality of wires simultaneously. The work coil 3' may be of any desired multiple form, there being two coils here shown arranged in parallel and longitudinally and co-axially of each other, and with a pair of spaced posts 19 therelbetween to serve as a guide means for the plurality of wires. The same form of guide means 20 and 2| is located at the ends of the multiple induction coil for the passage of the wires therebetween. All of the wires, prior to passing through the guides means 2!] and after passing through the guide means 2|, will be guided individually between sets of posts 22 and 23, respectively; in this way, the wires may be moved separately both before and after the heating operation and may be guided more emciently through the induction coil in more compact and effective manner, possibly in contactual relation to each other, so as to thereby increase the heating efficiency of the device.

This provision of an extended work circuit not only affords a longer heating period for the work but also this arrangement reduces the inductive reactive effect of the total work circuit and permits operation at higher and more efficient frequencies; or, with a given frequency, there may be employed a longer work circuit, the length of time of the wire in the work circuit being animportant factor. Also, it should be-noted that with the addition of every parallel coil, the coupling becomes closer and there is a further advantage in the parallel arrangement of the coils.

It should be noted that a plurality of any of the forms of guide means may be arranged in parallel: none of the guide means herein disclosed is limited to being employed in a single form. The employment of a plurality of induc tive forms, arranged in parallel, decreases the inductive reactiv effects and thereby permits the generator to operate at higher frequencies or at a given frequency with a larger physical load or work circuit.

In Figs. 10 and 11 Ihave illustrated a rotatable cylindrical roller 24 of electric insulation material with a strip 24a of metal, as for instance copper, attached thereto and extending longitudinally thereof. This stripof metal 24a is provided with sets of notches through which the wires W, for instance, are intended to keep in proper form and to move with the roller 24. These sets of notches are suitably spaced from each other so that there will be substantial length of wire short-circuited in closed loops between its successive points of contact with the metal strip 240., this being a close coupling. The effective portion of this guide is of course located within the work coil 3, as in the case of all other forms of guide means herein illustrated and described, and the work will engage and leave the guide means at points outside of the field of induction so as to avoid any sparking. The guide roller 24 is rotated by and at the rate of movement of the work, thereby avoiding any relative movement between the work and the guide means. The effect of this particular form of guide means is to have closed circuits of the wires W within the field of induction, with the result that heating of the wires will be effected by conducted currents longitudinally through each of these shortcircuited sections of the wires, in addition to the heating of the wires by electric induction. Thus there is accomplished heating by both induced and conducted currents and it is also possible to heat-treat an increased extent of wire within a given longitudinal extent of the guide means. This form of guide means comprises, in effect, a plurality of sections for progressively heating the wires.

Figs. 12 and 13 illustrate another form of device in which a guide body 25 of circular or other suitable cross section may have longitudinal grooves 25a upon the outside thereof and fillets 26 of magnetic material in these grooves, these fillets being in turn provided with grooves of proper dimension to receive the individual fine wires. The body of this guide means may be made of any suitable material that will withstand the heat to which it is subjected. With the arrangement disclosed in this form of device, there is obtained the benefit of the increased circumference about the fillets in each instance and, as a result, there is obtained relief from the ordinary hindrance to inductive heating of fine wires or other forms of work, as above pointed out. With this form of guide means there is obtained a loose coupling.

, extent of the guide means. 60.

In Figs. 14, 15 and 16 I have illustrated another form of guide means by which it is possible to subject a plurality of wires or other form of work to the heating effect of the induction coil 3 at one time and within a given longitudinal In this form of device, each individual Wire W, to be heated, is extended past a plurality of staggered metalposts which project radially from the outer surface of the cylindrical guide 2'! of electric insulation material. For instance, one of the moving wires W will move past and in electric contact with the posts A and A; another of the moving wires will extend past and in electric contact with the posts B and A; another of the moving wires will extend past and in electric contact with posts 18 and B; another of the moving wires will extends past and in electric contact with the posts A and J.

Each wire passes upon opposite connection with Figs. and 6 hereof.

sides of the two posts in each instance, as indicated in Figs. i l and 16; and the two wires, as they extend past the same post in each instance, do so at different elevation as indicated in Fig. 16. It is to be understood that in Fig. the circumference of guide is opened out into a flat plane for the purpose of more fully and clearly illustrating the arrangement of the posts and wires and their interengagement in the manner just explained. With this arrangement, the combined loop of wire will be heated by induced electrical energy and also by the resulting electrically conducted currents through the combined closed loop of the work, in each instance, just explained, thereby obtaining a close coupling.

By virtue of the increased circumferential extent of the wire or other form of Work in the field of electric induction, as above explained, it becomes possible for heavy electric currents to flowwithin the work, thereby facilitating the heating of the work. In fact, the heating is accomplished by both electrically induced and conducted currents, as above pointed out. A further advantage resides in the fact that, with my present invention, heating of a given piece of work to the required degree of temperature may be accomplished at frequencies that are substantially lower than would otherwise be required.

In Figs. 17 and 18 I have illustrated an em bodiment of my present invention in which the tuned induction tank coil has electric inductive relation within the single-turn copper loops 3|, each with its ends attached to the oppositely disposed copper plates 32. The plates 32 at their opposite ends are connected to the parallel portions of the copper inductor body which is formed with a substantially cylindrical portion 34. The portion 34 is formed upon its inner surface with a plurality of parallel longitudinal grooves for accommodating the plurality of separate wires, rods or strips of metal, indicated by reference letter W, which are to be heated, this form of work-holding and work-guiding body to be regarded as an electrical guide block. Within this guide block there may be provided a core of electric insulation material 35 to ensure that the wires W or the like remain in their individual grooves as they pass therethrough during the heating operation. is provided between the parallel portions 32 and 33. This particular form of device is especially adapted for high amperage and low voltage of current and hence may be referred to as a heavyduty form of device; and this same type of device may be designed also for other manners of handling the work while passing through the same, for instance those herein described in As the wire or other work is drawn along the copper block in direct electric contact. there is obtained heating of the same by electric induction and electric conduction at very close coupling. This form of device he water-cooled, as indicated in a general way by reference numeral 36.

Thus I have devised an invention which is capable of accomplishing the various objects noted above in connection with the heat-treatment of fine wires, bars and strips of metal. In addition to the several advantages flowing from this invention, as above briefly noted, it is believed. that further advantages will suggest themselves to those who are familiar with the art towhich the present invention relates.

Electric insulation material What I claim is:

1. In the method of heat-treating metal wire or the like, the step of directing the same 1ongi tudinally through and in electro-conductive'relation to a stationary guide means of low electrical resistivity in a uniformly close field of electric induction so as to subject the Wire or the like directly to electric induction and electric conduction in a uniform manner both circumferentially and longitudinally of the wire or the like while maintaining the guide means at low temperature compared with that to be developed in the metal wire or the like.

2. In the method of heat-treating metal wire or the like, the step of directing the same longitudinally through and in electr c-conductive relation to a stationary guide means of such character with respect to the work as to produce permeability change therebetween in a uniformly close field of electric induction so as to subject the wire or the like directly to electric induction and electric conduction in a uniform manner both circumferentially and longitudinally of the Wire or the like while maintaining the guide means at low temperature compared with that to be developed in the Wire or the like.

3. In the method of heat-treating metal wire or the like, the step of directing the same longitudinally through a stationary guide in a uniformly close field of electric induction and simultaneously subjecting the same directly thereto in a uniform manner both circumferentially and longitudinally of the wire or the like and to electric conduction with respect to said guide while maintaining the guide at low temperature compared with that to be developed in the wire or the like.

4. In the art of heat-treating metal wire or the like, a stationary guide means of low electrical resistivity as compared with that of the wire or the like for directing the wire or the like through a field of electric induction, said guide means being completely closed circumferentially throughout the entire longitudinal extent thereof so as to permit uninterrupted current flow about a unidirectional path circumferentially therein and being provided with laterally open and open-end groove means in a surface thereof for positioning the wire or the like in electro-conductiv relation to said guide means and maintaining the same in predetermined position while passing through a field of electric induction.

5. In the art of heat-treating metal wire or the like, a stationary guide means for directing the wire or the like through a field of electric induction, said guide means including a body that is completely closed circumferentially throughout the entire longitudinal extent thereof so as to permit uninterrupted current flow about a unidirectional path circumferentially therein and is of integral one-piece form throughout and of comparatively low electrical resistivity with respect to that of the Wire or the like and that has a plurality of longitudinally extending laterally open and open-end grooves provided in a surface thereof and arranged about the longitudinal axis of said body for positioning the wire or the like in electro-conductive contactual engagement therewith and for maintaining the same in predetermined position.

6. In the method of heat-treating metal wire or the like, the step of directing a plurality of metal wires or the like simultaneously longitudinally through and in electric-conductive relation to a stationary guide means of low electrical resistivity as compared with the wires or the lik in the same uniformly close field of electric induction so as to subject the Wires or the like directly to electric induction and electric conduction in a uniform manner both circumferentially and longitudinally of the wires or the like While maintaining the guide means at low temperatur compared with that to be developed in the Wires or the like.

7. In the method of heat-treating metal wire References Cited in the file of this patent UNITED STATES PATENTS Number 15 Number Name Date Spire Sept. 1, 1931 Northrup Mar. '7, 1933 Simons et a1. May 12, 1936 Simons June 1, 1943 Wilson May 23, 1944 Schneider et al Sept. 18, 1945 Arndt July 15, 1947 Marien et a1. Dec. 1, 1951 FOREIGN PATENTS Country Date Great Britain Jan. 10, 1947 Great Britain Jan. 14, 1949 Great Britain Jan. 17, 1949 

